Distributed adaptive CCA mechanisms

ABSTRACT

A method implemented by a first network device where the method provides an adaptive clear channel assessment (CCA) by collecting a neighboring network device set for a wireless local area network (WLAN). The method detects a wireless signal from a second network device on a wireless medium. A signal quality of the wireless signal is then determined. An identity of the second network device is also determined. The second network device is then added to the neighboring network device set of the first network device, in response to determining that the second network device is a neighbor based on the signal quality of the wireless signal.

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/049,800, filed on Sep. 12, 2014, U.S. Provisional PatentApplication No. 62/074,544 filed Nov. 3, 2014, and U.S. ProvisionalPatent Application No. 62/080,033 filed Nov. 14, 2014.

FIELD OF INVENTION

The embodiments described herein are related to the field of wirelesslocal area network (WLAN) operation. More specifically, the embodimentsdescribed herein relate to a method and system for an adaptive thresholdprocess and collection of a neighboring network device set for improvingthe efficiency in assessing the availability of the wireless medium forcommunication amongst a set of network devices. Other embodiments arealso disclosed.

BACKGROUND

Institute of Electrical and Electronics Engineers (IEEE) 802.11 is a setof physical and media access control (MAC) specifications forimplementing wireless local area network (WLAN) communications. Thesespecifications provide the basis for wireless network products using theWi-Fi brand managed and defined by the Wi-Fi Alliance. Thespecifications define the use of the 2.400-2.500 GHz as well as the4.915-5.825 GHz bands. These spectrum bands are commonly referred to asthe 2.4 GHz and 5 GHz bands. Each spectrum is subdivided into channelswith a center frequency and bandwidth. The 2.4 GHz band is divided into14 channels spaced 5 MHz apart, though some countries regulate theavailability of these channels. The 5 GHz band is more heavily regulatedthan the 2.4 GHz band and the spacing of channels varies across thespectrum with a minimum of a 5 MHz spacing dependent on the regulationsof the respective country or territory.

Communication on unlicensed spectrums, such as any given channel ofeither the 2.4 GHz or the 5 GHz bands, between network devices of theWLAN utilizes the clear channel assessment (CCA) protocol. CCA isdefined in the IEEE 802.11 standard as part of the Physical MediumDependent (PMD) and Physical Layer Convergence Protocol (PLCP) layer.CCA is composed of two related functions, carrier sense (CS) and energydetection (ED).

Carrier sense (CS) refers to the ability of the receiver to detect anddecode an incoming Wi-Fi signal preamble. In addition, CCA must bereported as Busy when another Wi-Fi signal preamble is detected, andmust be held as Busy for the length of the received frame as indicatedin the frame's PLCP Length field. Typically, any incoming Wi-Fi framewhose PLCP header can be decoded will cause CCA to report the medium asBusy for the time required for the frame transmission to complete.

The PLCP header Length field indicates either the number of microsecondsrequired for transmission of the full frame MAC protocol data unit(MPDU) payload, or the number of octets carried in the frame MPDUpayload which is then used in combination with the Rate field (whichidentifies the modulation used for the payload) to determine the timerequired for MPDU transmission. In any case, the length or rate+lengthfields of the MPDU give the receiver the information required tode-modulate the frame and determine how long the wireless medium will bebusy.

Energy detection (ED) refers to the ability of the receiver to detectthe energy level present on a given channel where a discernable Wi-Fipreamble cannot be decoded. ED is based on the noise floor, ambientenergy, interference sources, and unidentifiable Wi-Fi transmissionsthat may have been corrupted but can no longer be decoded. ED cannotpredict the exact length of time the wireless medium will be busy,instead ED must sample the wireless medium in every slot time todetermine if the energy still exists. ED utilizes a threshold levelabove which the detected energy level must exceed before the wirelessmedium is classified as busy or idle. This minimum threshold level canbe referred to as the ED threshold level or CCA sensitivity level. TheCCA sensitivity level is usually much lower for valid Wi-Fi signals thatcan be decoded using CS than it is for other signals where a discernablepreamble cannot be decoded.

Received signal strength indication (RSSI) is another measurement of theenergy or power present in a received radio frequency (RF) signal thatis generated by devices implementing IEEE 802.11. The units for RSSIvalues are not specified and can have an arbitrary range where a greaterRSSI value indicates a stronger signal. However, a reference power levelis usually considered, such as 1 mW, and the received power level of asignal is compared to the reference level, such as the ratio of thereceived signal power level to the reference power level. If such ratiois expressed as a logarithmic level, the dBm unit for power level isobtained. The RSSI value can be utilized in processes such as therequest to send/clear to send (RTS/CTS) exchange process to identify inconjunction with other factors when a wireless medium is Idle.

SUMMARY

The embodiments encompass a method implemented by a first network devicewhere the method provides an adaptive clear channel assessment (CCA) bycollecting a neighboring network device set for a wireless local areanetwork (WLAN). The method detects a wireless signal from a secondnetwork device on a wireless medium. A signal quality of the wirelesssignal is then determined. An identity of the second network device isalso determined. The second network device is then added to theneighboring network device set of the first network device, in responseto determining that the second network device is a neighbor based on thesignal quality of the wireless signal. Further, a set of signal qualityvalues for the neighbor network device are collected and stored for aparticular duration or number of received frames from the neighbornetwork device.

In another embodiment, a method is implemented by a first network deviceto provide the CCA process in the WLAN to determine an availability of awireless channel in the WLAN. The method includes detecting, by thefirst network device, a wireless signal from a second network device ona wireless medium. It is determined whether a target network device ofthe wireless signal is a neighbor of the first network device. Then atarget device threshold is compared against an average of the set ofsignal quality values associated with the target network device inresponse to determining that the target network device is a neighbor ofthe first network device. When the average signal quality value is abovethe target network device threshold, the wireless medium/channel isdetermined to be busy. Otherwise, when the average signal quality valueis below the target network device threshold, the wirelessmedium/channel is determined to be idle.

In a further embodiment, a network device implements a method to improveefficiency for CCA in the WLAN. The network device includes anon-transitory machine readable medium having stored therein an adaptivethreshold module, and a processor coupled to the non-transitory machinereadable medium, the processor configured to execute the adaptivethreshold module, the adaptive threshold module configured to detect awireless signal from a second network device on a wireless medium, todetermine a signal quality of the wireless signal, to determine anidentity of the second network device, and to add the second networkdevice to the neighboring network device set of the first networkdevice, in response to determining that the second network device is aneighbor based on the signal quality of the wireless signal. Theadaptive threshold module may also be configured such that a set ofsignal quality values for the neighbor network device are collected andstored for a particular duration or number of received frames from theneighbor network device.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that differentreferences to “an” or “one” embodiment in this specification are notnecessarily to the same embodiment, and such references mean at leastone. Further, when a particular feature, structure, or characteristic isdescribed in connection with an embodiment, it is submitted that it iswithin the knowledge of one skilled in the art to affect such feature,structure, or characteristic in connection with other embodimentswhether or not explicitly described.

FIG. 1 is a diagram of one embodiment of a WLAN that illustrates anexample of possible issues related to the use of adaptive thresholdprocesses.

FIG. 2 is a flowchart of one embodiment of a process for generating aneighboring network device set.

FIG. 3 is a flowchart of one embodiment of the adaptive thresholdprocess.

FIG. 4 is a diagram of a network device implementing a station or accesspoint that executes an adaptive threshold process.

FIG. 5 is a schematic block diagram exemplifying a transmitting signalprocessor in a WLAN device.

FIG. 6 is a schematic block diagram exemplifying a receiving signalprocessing unit in the WLAN.

FIG. 7 is a diagram of an example wireless local area network.

FIG. 8 is a timing diagram providing an example of the CSMA/CAtransmission procedure.

FIG. 9 is a diagram of a very high throughput (VHT) PPDU utilized by aWLAN device PHY layer.

FIG. 10 is a table of the fields of the VHT PPDU.

DETAILED DESCRIPTION

The embodiments provide a method and system for wireless mediumassessment implemented by a network device (e.g., a station such as anaccess point) in a wireless communication system such as a wirelesslocal area network (WLAN) implementing IEEE 802.11. The method includescollecting and maintaining information about nearby network devices inthe wireless communication system by measuring the signal quality (e.g.,received signal strength indicator (RSSI), energy level, signal-to-noiseratio, or similar metrics) of received frames from such network devices.The method utilizes this information about nearby network devices toimplement an adaptive threshold (e.g., a clear channel assessment (CCA)threshold) process during subsequent transmissions. This adaptivethreshold process uses multiple thresholds to increase the likelihood oftransmission over a wireless medium by the network device. The adaptivethreshold process includes safeguards to ensure that the transmissionsof the network device will not interfere with its neighbors whenassessing whether a shared wireless medium, such as a wireless channelor set of wireless channels, is in use (e.g., Idle or Busy). A ‘set,’ asused herein refers to any positive whole number of items. The method mayidentify neighbors of a given network device by monitoring thecommunications of the neighbors on the shared wireless mediums. Thismonitoring can include identifying a target receiver and/or a sourcetransmitter of each frame that is received during the wireless mediumassessment.

When the network device seeks to transmit over a wireless medium, acheck is made whether there is any current transmission and if sowhether the current transmission is directed at a neighbor of thenetwork device. The process may also take into account a signal qualityvalue/level of the transmission. If the received frames are not directedat a neighbor of the network device and/or the received frames have asignal quality value/level below an adaptive threshold (e.g., a CCAthreshold), then the network device may deem the wireless mediumavailable for transmission if other potential qualifying conditionsrelated to the likelihood of interfering with the communication ofneighboring nodes on the wireless medium are met.

In the following description, numerous specific details are set forth.However, it is understood that embodiments may be practiced withoutthese specific details. In other instances, well-known circuits,structures and techniques have not been shown in detail in order not toobscure the understanding of this description. It will be appreciated,however, by one skilled in the art that the embodiments may be practicedwithout such specific details. Those of ordinary skill in the art, withthe included descriptions, will be able to implement appropriatefunctionality without undue experimentation.

References in the specification to “one embodiment,” “an embodiment,”“an example embodiment,” etc., indicate that the embodiment describedmay include a particular feature, structure, or characteristic, butevery embodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to effect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

In the following description and claims, the terms “coupled” and“connected,” along with their derivatives, may be used. It should beunderstood that these terms are not intended as synonyms for each other.“Coupled” is used to indicate that two or more elements, which may ormay not be in direct physical or electrical contact with each other,co-operate or interact with each other. “Connected” is used to indicatethe establishment of communication between two or more elements that arecoupled with each other. A “set,” as used herein refers to any positivewhole number of items including one item.

The operations in the flow diagrams will be described with reference tothe exemplary embodiments of the other figures. However, it should beunderstood that the operations of the flow diagrams can be performed byembodiments other than those discussed with reference to the otherfigures, and the embodiments discussed with reference to these otherfigures can perform operations different than those discussed withreference to the flow diagrams.

An electronic device stores and transmits (internally and/or with otherelectronic devices over a network) code (which is composed of softwareinstructions and which is sometimes referred to as computer program codeor a computer program) and/or data using machine-readable media (alsocalled computer-readable media), such as non-transitory machine-readablemedia (e.g., machine-readable storage media such as magnetic disks,optical disks, read only memory, flash memory devices, phase changememory) and transitory machine-readable transmission media (also calleda carrier) (e.g., electrical, optical, radio, acoustical or other formof propagated signals—such as carrier waves, infrared signals). Thus, anelectronic device (e.g., a computer) includes hardware and software,such as a set of one or more processors coupled to one or morenon-transitory machine-readable storage media (to store code forexecution on the set of processors and data) and a set of one or morephysical network interface(s) to establish network connections (totransmit code and/or data using propagating signals). Put another way, atypical electronic device includes memory comprising non-volatile memory(containing code regardless of whether the electronic device is on oroff) and volatile memory (e.g., dynamic random access memory (DRAM),static random access memory (SRAM)), and while the electronic device isturned on that part of the code that is currently being executed iscopied from the slower non-volatile memory into the volatile memory(often organized in a hierarchy) for execution by the processors of theelectronic device.

A network device is an electronic device that communicativelyinterconnects other electronic devices on the network (e.g., othernetwork devices, end-user devices). Some network devices are “multipleservices network devices” that provide support for multiple networkingfunctions (e.g., routing, bridging, switching, Layer 2 aggregation,session border control, Quality of Service, and/or subscribermanagement), and/or provide support for multiple application services(e.g., data, voice, and video). Network devices or network elements caninclude stations and access points in wireless communications systemssuch as wireless local area network (WLAN) including WLANs implementingIEEE 802.11. Stations are devices connected to and communicating in aWLAN including client or user devices that connect to the WLAN viaaccess points. Access points are network devices that may be specializedwireless access points that can communicate with other network devicesin the WLAN via the wireless medium or via wired connections.

IEEE 802.11 based WLAN systems rely on Clear-Channel-Assessment (CCA),in the physical layer (PHY) that determines the current state of use ofthe wireless medium (WM), such that a station will access a givenwireless channel only when the WM becomes idle (i.e. there is notransmission on the wireless medium and other qualifying conditions aremet). Some CCA rule mechanisms, for example some of the rule mechanismsdefined in IEEE 802.11, indicate that the primary channel is Busy, ifone of the conditions listed in Table I is met, otherwise the primarychannel is determined to be Idle. If the primary channel is idle, thenthe PHY layer will check the secondary channels.

TABLE I Operating Channel Width Conditions 20 Mhz, 40 MHz, The start ofa 20 MHz NON_HT PDU in the 80 MHz, 160 MHz primary 20 MHz channel asdefined in or 80 + 80 MHz 18.3.10.6 (CCA requirements). The start of anHT PPDU under the conditions defined in 20.3.21.5 (CCA sensitivity). Thestart of a 20 MHz VHT PPDU in the primary 20 MHz channel at or above −82dBm. 40 MHz, 80 MHz, The start of a 40 MHz non-HT duplicate or 160 MHzor VHT PPDU in the primary 40 MHz channel at 80 + 80 MH z or above −79dBm 80 MHz, 160 MHz The start of an 80 MHz non-HT duplicate or or 80 +80 MHz VHT PPDU in the primary 80 MHz channel at or above −76 dBM 160MHz or 80 + The start of a 160 MHz or 80 + 80 MHz non- 80 MHz HTduplicate or VHT PPDU at or above −73 dBM

However, with the increased demand on WLANs there is a need for moreaggressive channel access, which requires increasing the CCA thresholdvalue, to increase system throughput. However, increasing the CCAthreshold value may result in more frequent packet collision anddegradation of Quality of Service (QoS) of packet delivery.

WLAN communication systems are being deployed in diverse environments.These environments are characterized by the existence of many accesspoints (AP) and non-AP stations in geographically limited areas.Increased interference from neighboring network devices gives rise toperformance degradation. Additionally, WLAN devices are increasinglyrequired to support a variety of applications such as video, cloudaccess, and offloading. In particular video traffic is expected to bethe dominant type of traffic in many high efficiency WLAN deployments.With the real-time requirements of some of these applications, WLANusers demand improved performance in delivering their applications,including improved throughput requiring improvements in the availabilityof the wireless medium.

In this regard, when a station (STA) is transmitting a packet over thewireless medium, nearby STAs are not allowed to transmit to preventcollisions from happening. The area that nearby STAs are prohibited isdetermined by the CCA sensitivity or threshold value. In a dense WLANenvironment, which is a target of WLAN development, a CCA thresholdvalue (−82 dBm for 20 MHz) might be too conservative in some scenariossuch that transmission efficiency is diminished or sub-optimal. Toenhance the WLAN system throughput and network efficiency, increasingthe CCA threshold value is a possible solution. However, simplyincreasing the CCA threshold value (i.e., lowering CCA sensitivity) maycause other problems that may in some instances degrade networkperformance. The CCA threshold value is used herein as a value of CCAsensitivity representing a current signal quality level above which asignal must reach to render an associated wireless channel busy.

If the CCA threshold value is increased in a WLAN, transmissionthroughput could be increased, because each STA can be more aggressivein assessing the wireless medium, and thus the STA may transmit a framemore frequently, however, this more aggressive transmission scheme mayoccur even though there is a frame already occupying the wirelessmedium. This can result in an increased probability of packet collision,and can result in severe performance degradation under somecircumstances or configurations such as for cell edge STAs.

Wireless communications systems and network devices implementing IEEE802.11 are provided by way of example and not limitation. One ofordinary skill in the art would understand that other similar wirelesscommunication technologies can apply the principles and structuresdescribed herein. Similarly, the use of a CCA threshold is given as themeasure for wireless medium availability assessment by way of example.However, any adaptive threshold associated with a measure of signalquality can be utilized consistent with the principles and structuresdescribed herein.

FIG. 1 is a diagram of one embodiment of a WLAN that illustrates anexample of possible issues of increasing an adaptive threshold value. Asshown in this figure, when a first network device (e.g., station (STA0))seeks to transmit a frame to a second network device (e.g., STA8), othertransmissions between network devices in the vicinity of the firstnetwork device may affect the availability of the shared wirelessmedium. The diagram illustrates different scenarios for possibletransmissions that may affect the first network device's ability toutilize the wireless medium. These scenarios are affected by theadaptive threshold utilized by the first network device. In the exampleof FIG. 1, a first threshold is illustrated as a solid line (e.g., a 82dBm threshold) and a second threshold is illustrated as a dotted line(e.g., a −72 dBm threshold). All network devices within the radius of athreshold may be considered to be neighbors of the network device inassociation with the threshold. Thus, increasing a threshold may reducethe number of neighbors and may inversely increase the number of networkdevices that may be impacted by the transmission of the first networkdevice.

Without the benefit of the embodiments disclosed herein, a networkdevice, in the illustrated example STA0, will generally assestransmissions on a wireless medium as not impacting its decision totransmit if they fall below the threshold. For example, STAs 11-14 areall positioned such that their transmissions are below a standardthreshold (e.g., a −82 dBm CCA threshold). Any metric or measurement ofsignal quality can be utilized for the assessment of whether a networkdevice meets or exceeds a threshold. In such an implementation, anytransmission of STAs 11-14 would be ignored by STA0. However,transmissions of STAs 1-10 would affect (likely prohibiting) the abilityof STA0 to transmit over a shared wireless medium when using a −82 dBmCCA threshold. Increasing the threshold (e.g., to a −72 dBm CCAthreshold) excludes a greater number of network device transmissions(e.g., STAs 1-6) from consideration. However, there can be an adverseimpact in particular on network devices in closer proximity (e.g., STAs8-10) in terms of collision when these network devices are the targetdestinations of the transmissions of source network devices that arebelow the threshold. For example, the transmissions between STA2 andSTA9 in the illustrated example of FIG. 1 may be problematic when adecreased CCA threshold is used. The embodiments seek to avoid suchcollisions by tracking the neighboring network devices and avoidingtransmission when there is a transmission targeting these neighbornetwork devices. This policy can be applied regardless of the threshold.For example, this could be applied in the case of the transmissionbetween STA 4 and STA 3 using the standard threshold in this example.

The consideration of when a network device transmits may not be solelydependent on the determination of transmission signal quality or whetherthe target of the transmission on the wireless medium is a neighboringnetwork device. Other considerations can be based on the protocols andformat of the data and control message exchanges using the wirelessmedium. For example, the process can await expiration of distributedcoordination function (DCF) interframe spacing (IFS)(DIFS), performanceof a backoff, and similar interframe spacing considerations. Theembodiments for adaptive threshold systems and processes provideadditional criteria for determining whether a wireless medium isavailable for transmission by the network device seeking to transmitdata. The additional criteria is based on the use of the sourcetransmitting information and/or target receiver information of a framethat occupies the wireless medium when the network device performs achannel assessment process such as CCA. For this purpose, a networkdevice can maintain a set of neighboring network devices in a WLAN,wherein the set comprises information on network devices that the firstnetwork device's pending transmission may interfere with. When the firstnetwork device assesses the wireless medium (e.g., via CCA), even thougha received signal quality level for a frame currently occupying thewireless medium is below a threshold, the first network device may notbe allowed to access the medium in accordance with the processes for theadaptive threshold described herein, for example if information of thetarget receiver of the frame matches with a network device within theset of tracked neighboring network devices.

There can be multiple different embodiments for maintaining the set ofneighboring network devices (e.g., stations including access points in aWLAN) consistent with the basic concept mentioned above, which will beexplained below. One of ordinary skill would understand that theembodiments provided herein are made by way of example and notlimitation and that other variations to these embodiments are within thescope of this disclosure.

In one example embodiment, CCA is utilized to assess whether the sharedwireless medium is available. The CCA threshold is fixed in current IEEEamendments. However, it certain scenarios it may be better to adapt aCCA threshold, for each basic service set (BSS), to an optimum levelthat depends on the locations of the network devices in the WLAN, suchas the locations of STAs vs the access point (AP), and neighboringBSS/overlapping BSS (OBSS). For instance, in a BSS where the STAs areclose to the AP, the STAs would backoff if they receive a frame from anynode within their default −82 dBm coverage. However, given the locationof the nodes in this BSS, they can adopt a CCA threshold that is greaterthan −82 dBm as long as the AP receives signals from all its STAs abovethe adapted CCA threshold and as long as STAs defer to each other basedon the adapted CCA value.

Adapting the CCA level should consider potential STAs nearby. In a casewhere two BSSs (operating in the same frequency) are relativelydisjoint, adopting a CCA greater than −82 dBm by either BSS is lesslikely to hurt the operation of the other BSS significantly (forinstance in apartment complexes and similar crowded environments), butthis is not always the case.

An immediate consequence of a less sensitive CCA threshold is additionalhidden nodes that appear, which are nodes that are unknown to atransmitting STA. All the classical problems and solutions for dealingwith hidden nodes apply to the newly introduced hidden nodes. Thus, theembodiments described herein provide processes and systems that avoidadditional problems, such as collisions, higher interference, andsimilar problems that result from an aggressive CCA, which affects thenewly introduced hidden nodes.

FIG. 2 is a flowchart of one embodiment of the neighboring networkdevice set management process. This example embodiment provides oneembodiment of the neighboring network device tracking of the adaptivethreshold process and more specific implementation examples are given inrelation to the neighbor network device tracking process. The methoddescribed with relation to FIG. 2 is implemented by a network device,such as a station (including an access point or a client station) in aWLAN. Implementation is on a network device by network device basis.Each network device that is configured to use an adaptive CCA thresholdneeds to know about its neighboring network devices (i.e., neighboringSTAs in the WLAN) so that the network device avoids adopting lesssensitive thresholds (e.g., CCA thresholds) than the signal quality ofthe frames destined to those neighboring network devices. To know aboutits surroundings, each network device monitors the frames that itreceives and registers the transmitting address (TA) of those frames.The embodiments introduce this TA information into the physical layer(PHY) header in the full TA format or in a shortened format. In someembodiments, the TA information can be presented as any one of a numberof shorter forms of STA identification, or similar network deviceidentification, which can be conveyed inside a signal field of thePHY/physical layer convergence procedure (PHY/PLCP) header. Examples ofsuch identifications are AID (association ID), PAID (partial associationID), PBSSID (partial BSS ID), and GID (group ID) in IEEE 802.11 ac, butthere could be new/alternate identifiers (IDs) based on other forms forshortening AID, BSSID, and similar identifiers. The full or shortrepresentation of the identities of the transmitting station of eachframe are registered (i.e., recorded in a set of tracked neighboringnetwork devices).

The implementing network device performs this neighboring network devicetracking process when it is awake (some network devices have an inactivemode such as a sleep mode). After some time, the network device realizeswhat network devices are in its neighborhood, based on appearance oftheir IDs in past received frames. In some embodiments, the receiving IDand transmitting ID of a network device can be assumed to be the same,or even if they are different (due to different number of bits, bitassignment or other reasons), then there is a known relationship betweenthese two IDs that can be verified by all network devices implementingthis adaptive threshold process. This means that all network devices canidentify whether a pair of transmitting and receiving IDs belong to thesame network device or not.

The set of neighboring network devices can be utilized for assessingwhether a wireless medium is idle. When a network device has formed sucha set, which is referred to as a neighboring network device set, theneighboring network device set can be checked when the implementingnetwork device receives a frame (which is not destined to the networkdevice itself). The network device decides whether the wireless mediumis available or not based on a set of factors including the identity ofthe receiving neighboring network device indicated in the frame and thesignal quality (e.g., an RSSI) of the transmitting network device, asdescribed further herein. However, in the adaptive threshold processeach network device is allowed to adapt the threshold (e.g., a CCAthreshold) if it has gathered a history of frame exchanges of itsneighbors for a minimum duration of time, or a minimum normalized numberof frame exchanges. This minimum history can be configured by anadministrator or similar entity to be any amount of time or number offrames. For example, power-saving STAs in WLANs may only be allowed touse adaptive CCA when they have observed the wireless channel longenough, i.e., their total awake time reaches the minimum duration oftime required. In some embodiments, there may be a maximum on the singlesleep time duration as well, where if a network device is in sleep modefor a duration of time longer than a given value, the network deviceresets its neighboring network device sets and starts anew because thecollected information is out of date or stale.

In one embodiment, the neighboring network device set management processis initiated at the network device in response to detecting a wirelesssignal from a second network device on a wireless medium (Block 201).For example, a network device, such as a WLAN device implementing anadaptive threshold process such as an adaptive CCA process andneighboring network device set management process, may implement thisprocess. The implementing network device can be any station including anon-AP station or an AP. Referring to the example wireless communicationsystem of FIG. 1, the implementing network device STA0, detects thetransmission between other stations on the shared wireless medium suchas any one of the transmissions between STA7 and STA10, STA2 and STA9,STA4 and STA3, STA14 and STA1, and STA5 and STA11. While the Figureshows these transmissions as seemingly simultaneous, one skilled in theart would understand that if the transmissions are on a shared wirelessmedium, and if the transmitting STAs are within each other's coverage,then only non-interfering transmissions in a WLAN that operate based onthe IEEE 802.11 specification could be taking place at any given time.The different transmissions are shown for sake of illustrating differingtransmission scenarios.

The signal quality of the received wireless signal can then bedetermined (Block 203). For example, the STA0 can determine an RSSI,signal to noise ratio, ED level or similar measure of the quality of thewireless signal transmitting the received frame to be utilized todetermine the proximity of the transmitting STA (i.e., neighbor statusof the transmitting STA relative to STA0). In some embodiments, thesignal quality is taken as an average of the signal quality over anyperiod of time or number of frames received from a given network deviceor as an average signal quality during the last unit of observationinterval.

The wireless signal is then examined to determine the identity of thesecond network device (Block 205). The information in the receivedwireless signal, e.g. a received frame, can comprise any combination ofAID, PAID, MAC address, BSSID, Partial BSSID, GID, and/or similaridentifier for either the transmitting network device that is in the PHYheader and thereby enables the identification of the transmittingnetwork device and maintenance of the neighboring network device setwithout having to decode other information in the transmission such asMAC layer information. Similarly, the received wireless signal can haveadditional information collected relating to the timing and similarcircumstances of its transmission (Block 207). For example, the processcan record the latest time stamp when each ID appeared in any receivedframe, the number of instances per unit time that the ID appeared incaptured frames, and similar information. This information is collectedto update the tracking of such metrics associated with each neighboringnetwork device ID. In some embodiments, a history of the past T seconds,T being any positive number of seconds, can be maintained where thenetwork device has recorded the frames exchanged by its neighboringnetwork devices. This history can be used to compute a moving average orsimilar computation for assessing signal quality instead of using a mostrecent signal quality to avoid having an inaccurate signal qualitydetermination affect the neighboring network device set managementprocess. Using a moving average of the signal quality, if theneighboring network devices move out of the neighborhood their presenceis gradually removed from the neighboring network device set or even iftracked they may be excluded from those network devices consideredneighbors. In some embodiments, the neighboring network device set islimited to those network devices within a particular proximity using anymetric (e.g., RSSI within a CCA threshold). However, in otherembodiments, neighboring network devices outside the threshold area arealso tracked, but do not factor into computations related to identifyingneighbors. For example, some network devices may move into and out ofthe proximity of the network device or have varied readings near theborder of the proximity. In such cases, in particular where a movingaverage is used for the signal quality, the history may include signalquality values that are both within and outside of a given threshold forconsidering an associated network device as a neighbor. Thus, a networkdevice may be tracked that has a signal quality that is proximate to thethreshold or where there is at least one signal quality value in thehistory that meets the threshold.

A determination is then made whether the second network device is aneighbor of the implementing (first) network device (Block 208). In oneembodiment, a check may first be made to determine whether the signalquality of the wireless signal received from the second network deviceexceeds a threshold, such as the CCA threshold. Any metric for signalquality can be utilized as a threshold for deciding whether a networkdevice is a neighbor where the metric is generally indicative of thelikelihood of interference between the implementing network device andthe second network device when transmitting on the same channel. In someembodiments, multiple levels of thresholds can be utilized to createmultiple levels of neighborhood relationships. Each neighborhoodrelationship set may later be used to apply different adaptivethresholds based on a target receiver being in the respectiveneighborhood set. A basic CCA threshold is often −82 dBm where anywireless signal below this threshold is not identified as a neighboringnetwork device. A more aggressive CCA threshold (e.g., −72 dBm) could beutilized in some scenarios that enables greater granularity whenestablishing neighborhood sets and potentially enabling greater use ofthe wireless channel as described in FIG. 3 below. One skilled in theart would understand that the combination and the number of thresholdsusing any metric indicative of wireless signal strength or interferenceon a given channel between network devices can be utilized consistentwith the principles and structures of the embodiments described herein.If a network device is determined not to be a neighbor of theimplementing (first) network device based on properties of the wirelesssignal, then the wireless signal may be ignored during this process(Block 210).

However, if the wireless signal indicates that the second network devicedoes qualify as a neighbor (e.g., by exceeding a current threshold),then the process proceeds to determine whether the second network device(i.e., the transmitting network device) is already known to theimplementing (first) network device (Block 209). This can be done bylooking in the set of neighboring network devices maintained by theimplementing network device (i.e., it is known to the implementingnetwork device if the second network device is in the set of neighboringnetwork devices) by looking up the transmitting ID in a neighboringnetwork device set. If the second network device is known to theimplementing network device, then the process updates the information itmaintains about the second network device (Block 211). For example, ifthe transmitting network device is known to the implementing networkdevice then the existing transmitting network device entry in aneighboring network device set (e.g., a list or similar data structure)can be updated with all of the collected data. In one example, the entrycan be updated with a new signal quality reading, an updated averagesignal quality, updated time stamp information or a similar recordationcan take place. If the second network device is not known to theimplementing device, then the second network device is added to theneighboring network device sets (Block 213). For example, if there isnot an existing entry, then the process creates a network device entryusing the ID of the network device in the neighboring network deviceset. The neighboring network device set can be any type of datastructure, including a database, a simple list, a linked list or similardata structure. In this example, the network device entry can record anyidentification information, including the AID, PAID, MAC address (whichmay require further processing of the MAC layer of the frame), BSSID,Partial BSSID, or similar ID. The network device entry can also includesignal quality information, including the most recent signal qualitymeasurement (e.g., an RSSI value), an average signal quality value, orsimilar signal quality information. The network device entry can alsoinclude timing information such as recent timestamp information orsimilar information.

Although described as only including devices in the neighboring networkdevice set that are considered neighbors, in another embodiment theneighboring network device set may include all devices in the network orall devices that the implementing station has detected a frame, or alldevices that the implementing network device has detected as a targetdevice in a frame. In these embodiments, the neighboring network deviceset may indicate which devices are considered neighbors and a confidencelevel associated with this determination. Also in these embodiments, theneighboring network device set may indicate which devices haveconsistently appeared as a target device in detected frames but no frameor few frames have been detected from these devices, where in such casesthe implementing device indicates such devices as non-neighbor devicesand associates a confidence level with this determination.

Returning to the example of FIG. 1, where STA0 is the implementing STA.When STA0 is awake, it records the relevant IDs (TA/RA or PAIDs/BSSIDsand their short forms that might appear in PHY/PLCP header) of theframes that STA0 captures. STA0 establishes the known relationshipbetween the transmitting and receiving IDs (PAID/PBSSID and/or the shortforms of the AIDs or the short forms of the AID of the second and thirdSTAs). This relationship can be stored in the neighboring network deviceset for devices that are determined to be neighbors of STA0. Theneighboring network device set is gradually updated whenever new IDs arecollected for neighbors of STA0. So after a given time period, STA0 willhave sufficient data for the transmit IDs related to STAs 1-10 thatappear on the frames it has captured and STA0 can infer that thesestations are nearby, i.e., within −82 dBm-coverage of STA0. Thisconstitutes the neighboring network device set for STA0. The use of aneighboring network device set or any data in it can be limited until aconfidence interval or period has elapsed that indicates sufficient timehas elapsed since the collection of information began to have a highconfidence that all neighboring network devices have been identified.

The embodiments for managing the neighboring network device set discussthe use of IDs for determining a transmitting network device and areceiving network device. In some embodiments this information isdetermined using a received frame in the form of a PPDU. These may beorthogonal frequency division multiplexing (OFDM)/orthogonal frequencydivision multiple access (OFDMA) PPDUs. Each OFDM/OFDMA PPDU has SIGsymbols (e.g. VHT SIG-A/B and HE SIG-A/B) where some ID of the recipientof the PPDU is indicated (e.g., PAID in case the recipient is a STA andPBSSID in case the recipient is an AP). In some embodiments, the PPDUformat can be modified to add some identification of the transmittingSTA to HE SIG-A/B in the PHY header. Depending on the number of bitsassigned to the receiving and transmitting IDs in the PHY header, exactor shorter IDs can be used.

If the same number of bits are assigned to the short mapping orrepresentations of the receiver/transmitter IDs (in HE SIG-A/B), then aSTA can be identified by PAID, and an AP is identified by PBSSID(regardless if they are the recipient or transmitter of the frame). Ifthe number of bits assigned to the short mapping or representations ofthe receiver and transmitter IDs are different, then: (a) as a recipienta STA is identified by PAID, and an AP is identified by PBSSID, and (b)as a transmitter a STA is identified by a shortened PAID (SPAID), and anAP is identified by a shortened PBSSID (SPBSSID). The PAID can have aone-to-one mapping with its shortened version, SPAID. Also, the PBSSIDcan have a one-to-one mapping with its shortened version, SPBSSID. Theone-to-one mapping is a priori known in the WLAN and all receiving STAscan establish the mapping between an ID and its shortened version. Insome embodiments independent BSS frames can also be utilized to collectdata about neighboring network devices. For IBSS frames, the networkdevices might use abbreviated representations of MAC frames so that theywould fit the limited bits available in the SIG symbols.

More specifically, the embodiments can include a revised SIG field suchthat both PBSSID and PAID or their shorter mappings can exist in the SIGfield. For example for downlink (DL) frames the configuration can bePAID (6 bits)+short PBSSID (SPBSSID) (3 bits), whereas currently in IEEE802.11 ac the PAID is 9 bits. For uplink (UL) frames the configurationcan be PBSSID (5 bits)+short PAID (SPAID) (4 bits), whereas currently inIEEE 802.1 lac/ah the PBSSID is 9 bits. In some embodiments, there is aunique relationship between PAID and its short mapping, and similarlybetween PBSSID and its short mapping such as a one-to-one mapping. Inthese embodiments, the SPAID can be obtained by using a hash functionover the corresponding PAID. Similarly, the SPBSSID can be obtained by aknown hash function over the PBSSID. Network devices can establish therelationship between PAID and SPAID, and BSSID and SPBSSID using a setof shared hash functions. By observing SPBSSID and SPAID and the knownhash function, the network devices can infer an identity of thetransmitter. With limited bits available for identifying thetransmitting and receiving network devices, there is a chance of IDcollision using hashing functions. Thus, the number of bits for SPAIDand SPBSSID can in some embodiments be optimized with a selection of ahash function dependent on the size of the wireless communicationnetwork or similar factors to limit collision probability.

In some embodiments, by introducing a sub-field in HE SIG-A/B thatcarries the identification of the transmitter of the frame, it may berequired that this identification is carried from the PHY entity to theMAC entity at each receiver for every received frame, and from the MACentity to the PHY entity at each transmitter for every frame. This isdone by introducing a parameter in TXVECTOR (sent from the MAC entity tothe PHY entity at the transmitter side) and RXVECTOR (sent from the PHYentity to the MAC entity at the receiver side). This parameter isdenoted by TXSTAID. When a non-AP STA sends a frame, it sets the TXSTAIDto SPAID, and when an AP sends a frame, it sets the TXSTAID to SPBSSID.Note that if the TXSTAID has the same length as PAID, then when a non-APSTA sends a frame, it sets the TXSTAID to PAID, and when an AP sends aframe, it sets the TXSTAID to PBSSID. When a STA receives a frame theSTA evaluates the TXSTAID that is carried in the frame to update itsneighboring network device set.

In the above embodiments, the identification appears in the PHY header(i.e. HE SIG-A/B) for sake of easier and less power-consuming processing(the PHY header format is described in further detail herein below). Insome instances, the MAC header may also include TA and RA addressessimilar to the above PHY IDs, this MAC header information can beutilized when a STA has taken the computational burden to decode thepayload.

As the result of above embodiments, the SIG symbol(s) that follows thePHY preamble in an IEEE 802.11 frame would have fields that identify thetransmitter and receiver identity, which could be a subset of thefollowing depending on whether the frame is a UL or DL frame or a frameexchanged in an IBSS: 1) PAID, 2) PBSSID, 3) short representation ofPAID, 4) short representation of PBSSID, 5) short representation of MACaddress of the transmitter, and 6) short representation of MAC addressof the receiver. The exact relationship between PAID and its shortrepresentation can be defined using a particular hash function or usingany other definition. Similarly, the exact relationship between PBSSIDand its short representation may be specified by any hashing function orsimilar relationship. Also, the exact relationship between a MAC addressand its short representation can be specified in a similar fashion. Theshort representation for each of the above IDs might have differentlength.

Also, in addition to the above SIG symbol(s) that follows the PHYpreamble in a frame, the frame might have other fields that facilitatethe adaptive threshold process. For instance, there might be a quantizedrepresentation of the transmit power of the transmitter of the frame.This representation could be a 2-3 bit representation or more whichidentifies the range of the transmit power of the transmitter. Also,there might be a field in one of SIG symbol(s) that follows the PHYpreamble in the frame that: (a) is set only by an AP, (b) functions asan indication as to whether the AP allows or disallows its associatedSTAs to use adaptive CCA rules. This field could be a single bit.

FIG. 3 is a flowchart of one embodiment of a process for application ofan adaptive threshold process. This process is an overview of anadaptive threshold process (e.g., an adaptive CCA process) as describedherein, where an implementing network device seeks to transmit on agiven wireless channel in a wireless communication system. The processcan be triggered in response to detecting a wireless signal from asecond network device on a wireless medium while attempting toaccess/assess the status of the wireless medium (Block 301). In oneexample, the process can be initiated by making a check to determinewhether the start of a frame is detected on a shared wireless medium(i.e., a frame is already being transmitted on the wireless medium, suchas a wireless channel, by another device). In this example, the receiverof the implementing network device can continuously monitor the wirelessmedium to detect frames on the wireless medium as part of a channelaccess process and/or carrier sensing process. In some embodiments, ifthere is no frame being transmitted on the wireless medium then theimplementing network device can transmit any queued frame, after backingoff according to the conventions specified in IEEE 802.11, such asenhanced distributed channel access (EDCA) or distributed coordinationfunction (DCF), because the wireless medium is considered not busy(idle) if other additional qualifications are met (i.e., Idle statequalifications are met).

A determination of the signal quality of the wireless signal maythereafter be performed (Block 305). In the example, if there is a framebeing transmitted (which can be determined from detecting a preamble inthe signal on the wireless medium), then the signal quality level of theframe being received on the wireless medium can be determined. Anymetric (e.g., RSSI or similar values) can be utilized as a signalquality level and any process can be utilized to identify the metric,including ED, CS, or similar measurement functions. In some instances,the frame cannot be discretely detected, but the signal quality of atransmitting signal can be detected and utilized.

A determination is then made whether the transmitting wireless signal(e.g., a frame) is coming from a distant station that would not bedisrupted by simultaneous transmission on the wireless medium. A checkis made whether the signal quality of the wireless signal (e.g., aframe) is below a threshold (e.g., a CCA threshold such as −82 dBm for a20 MHz channel) (Block 307). If the signal quality is below thisthreshold, then the signal originates too far away and the wirelessmedium is considered to be not busy (assuming a pre-determined periodwithout being busy has elapsed, e.g., after DIFS, after a backoff timeor similar conditions are met) (Block 303) enabling the transmission bythe first network device (e.g., an implementing station) of its own data(e.g., a queued frame). If the signal quality of the received frame isnot below the threshold, then a target network device (e.g., by lookingat the RX ID or similar information) of the received wireless signal isdetermined and a check is made whether a confidence level associatedwith the target network device has been reached (Block 310). Aconfidence level is a metric that is applied to the informationcollected about the neighboring network device set described herein andis specific to each tracked network device in the neighboring networkdevice set. Any confidence level metric or measurement can be utilizedthat indicates a predetermined number of received frames have beencollected in a given time period from the target network device suchthat an accurate representation of the target network device position orlikelihood of interference is known relative to the implementing networkdevice. The confidence level can be determined to be reached by lookingat the history of signal quality values of received frames for a targetnetwork device, by maintaining a counter of such signal quality valuesof the received frames or through use of a similar mechanism.

Additionally, the confidence level can be determined to be reached bylooking at the history of received frames. Where a large set of theframes have a network device as the target device of the frame but innone or a few frames the network device has appeared as the transmittingdevice of a frame, it may be determined that the device is not aneighbor with high confidence. If a confidence level associated with thetarget network device has not been met, then the wireless medium overwhich the wireless signal was received is determined to be busy (Block313). This ensures that a potential neighbor is not interfered with bythe implementing network device.

In some embodiments, when the target network device is not present inthe neighboring network device set, because no frames have been recentlyreceived from the target network device, or if the neighboring networkdevice set indicates that no frames have been recently received from thetarget network device, the implementing device may determine that thetarget network device is sufficiently far away and the medium is idle(not busy) (Block 303).

If the confidence level associated with the target network device hasbeen reached, then a check is made whether a target network device ofthe wireless signal (e.g., a target receiver of the received frame) is aneighbor (e.g., in the neighboring network device set) (Block 311). Ifthe target network device is not a neighbor (e.g., a target receiver ofthe received frame is not in the set), then the wireless medium isconsidered not busy (Block 303) or idle when related conditions are met(a pre-determined period without being busy has elapsed, e.g., afterDIFS, after a backoff time or similar conditions) and the implementingstation can proceed with the transmission of its queued frame.

If the target network device (e.g., a target receiver of the receivedframe) is a neighbor (e.g., it is in the nearby/neighbor station set),then a check is made whether a target network device threshold has beenexceeded by the signal quality values associated with the target networkdevice (Block 315). In embodiments with adaptive thresholds, the networkdevice utilizes this additional target network device threshold toassess whether the signal quality values that are tracked by theimplementing device indicate that transmitting on the wireless channelwould interfere with the neighbor network device that is the targetnetwork device of the received wireless signal. Thus, the adaptivethreshold and target network device thresholds are distinct andindependent thresholds. As used herein, a “threshold” generally refersto the adaptive threshold and the target network device or target devicethreshold is used to refer to this separate threshold for evaluatingwhether transmission would interfere with a neighbor network device. Anyset or combination of policies can be employed in determining whetherthe neighboring network devices exceeds the target network devicethreshold. If the target network device threshold is not exceeded, thenthe wireless channel is determined to be idle (Block 303). If the targetnetwork device threshold is exceeded by the signal quality value(s)associated with the target network device, then the wireless medium isconsidered busy (Block 313) and, in the example, the pendingtransmission of the queued frame of the implementing network devicewaits until the frame transmission completes and any reply completes. Itshould be noted that for purposes of this process the set of networkdevices that are considered neighbors may change along with the targetnetwork device and/or CCA threshold, where being within the CCAthreshold identifies neighbors or some similar criteria is used.

In the example of FIG. 1, given the list of neighbors in the neighboringnetwork device set has reached a confidence level, STA0 checks thereceiving ID of any captured frame with the neighboring network deviceset. If the receiving ID of the captured frame appears in theneighboring network device set, then STA0 can evaluate whether to usethe same standard sensitive CCA toward the captured frame and wait forthe end of the frame, evaluate the signal quality, e.g., as an averageRSSI that has been captured from destination network device in past Tmaxtime interval, and if the RSSI is smaller than a Tmax_RSSI value, theSTA might adapt to a less sensitive CCA toward the captured frame andeven might assume the medium is available and initiate the back offprocedure.

In some embodiments, the process includes the addition of an RXVECTORparameter denoted by RXRSSI which is sent from PHY entity to the MACentity for every frame that is received by the network device. A MACentity processes an RXRSSI parameter of the RXVECTOR of a frame asfollows. When the recipient of the frame is not the same network device,the MAC entity adds the RXRSSI value to the list of the RXRSSIs valuesreceived from the same network. This is particularly relevant where theneighboring network device set is constructed. In some embodiments, allthe previous RXRSSI values up to Tmax is stored for each transmittingnetwork device. In some other embodiments, all the previous RXRSSIvalues up to Tmax is averaged for each transmitting network device. Theaveraging function could be uniform averaging, or moving average whereolder RXRSSI values are gradually phased out of the average.

The embodiments can be configured to support the presence of legacydevices that do not support the modified SIG implementations. Whilereading SIG of the frames from neighboring network devices, each networkdevice would arrive at a conclusion of what percentage of the networkdevices around the computing device are legacy devices. For sake offairness toward legacy devices, it is important to apply a standardthreshold (e.g., a CCA threshold of −82 dBm) if there are more legacynetwork devices than a given threshold. Such a legacy threshold being anumber or percentage of legacy devices in a wireless communicationsystem such as WLAN. In order to gain more from the adaptive thresholdprocess (e.g., an adaptive CCA), an alternative is that the networkdevice optionally read MAC headers of the legacy frames, read the AIDsand process them with the same principle as outlined herein above, sothat the network devices can make decisions similar to the adaptivethreshold process described herein.

In some embodiments, the adaptive threshold process can be limited to DLapplications. Due to additional processing required by the suggestedproposal, one might suggest to limit the previously discussed proposalfor AP only, hence to allow only APs only to use adaptive CCA. Thiswould make sense due to larger percentage of DL vs UL in most WLANs. Insuch an example scenario, APs could adopt a CCA threshold greater than−82 dBm for frames that do not belong to the same BSS and likely theirintended receiver is not within the coverage of the AP. To perform suchprocessing in APs only, one approach is to use the embodiments describedherein above with the ID's in SIG (PAID and SPBSSID in DL frames, andBSSID and SPAID in UL frames) and let only APs change the CCAadaptively. In a further embodiment, the APs read the MAC header of allthe frames each receives and performs the adaptive CCA threshold processto find out whether there are nearby STAs that belong to other BSS ornot, and decide accordingly to whether to adapt the CCA threshold to begreater than −82 dBm for the frames that do not belong to the same BSS.Note that in this approach there is no need to have new IDs in SIG, i.e.the SIG would have the same ID's as before (PAID in DL and PBSSID in ULas in IEEE 802.11ac).

In some embodiments where shortened IDs are generated using hashingfunctions, some outcomes of the adaptive threshold process can beaffected. Due to the limited bits assigned to PAID and SPAID, it ispossible that two STAs have similar PAID or SPAID. However, what affectsthe outcome of the adaptive threshold process is if two STAs that are incoverage of each other and have the same PAID or SPAID. In general, ifthere are multiple STAs with the same PAID or SPAID it would cause otherSTAs to stick with a standard CCA threshold (e.g., −82 dBm) for thoseSTAs. This means that collision in IDs is not catastrophic and onlymakes other STAs more conservative.

In some embodiments, received wireless signals that are being processedmay have multiple destination. Frames that include multiple destinationscan include DL multiple user (MU) multiple in multiple out (MIMO)frames, or DL OFDMA frames. The criteria for handling such frames are amodification of the processes for single destination frames discussedabove. For such multiple destination wireless signals (e.g., frames),the network device obtains the potential recipient of the frames fromthe group identification. The group identification could be carried inan IEEE 802.11 ac-GID, or it could be carried in other forms, such asexplicitly identifying the set of recipients. Whatever the means ofgroup identification is, the network device obtains some knowledge ofthe potential recipients from the SIG fields within the MU MIMO PPDU orOFDMA PPDU. Upon obtaining such knowledge, network device checks whetherany of the potential destination network devices are within itsneighboring network device set. Thus, instead of checking for just asingle destination network device in the neighboring network device set,the process would check for each of the destination network devices. Ifnone of the potential recipient network devices are within theneighboring network device set, then the implementing device canconsider the wireless medium non busy and would be allowed to preparefor its own transmission if other conditions are met (e.g., DIFS andbackoff).

In some embodiments, if the implementing network device sees none of thepotential recipients have an average signal quality above a threshold(e.g., an RSSI larger than RSSI_Th) (i.e. the STAs could be within theneighboring network device list, but are far enough that they likelyreceive frames from STA0 with RSSI less than RSSI_Th), then networkdevice can consider the shared wireless medium non busy if otherconditions are met. If the receiving ID of the captured frame appears inthe neighboring network device set, then the implementing network devicecan be configured to use the same standard sensitive threshold (e.g.,CCA threshold) toward the captured frame and wait for the end of theframe, or evaluates the signal quality (e.g., the average RSSI that hasbeen collected captured the destination network device in past TBD_Tmaxtime interval, and if the RSSI is smaller than a RSSI_Th value, thenetwork device might adapt to a less sensitive threshold toward thecaptured frame and even might assume the medium is available andinitiates the back off procedure of other conditions are met.Alternatively, in some embodiments the network device always uses astandard sensitive threshold when it receives MU frame, any frame thattriggers transmission of MU frame such as Trigger frame, broadcastframes, or multicast frames.

In some embodiments, wireless signals may encompass the transmission offrames with larger than 20 MHz bandwidth: In these embodiments, thenetwork device identifies the availability of the primary 20 MHz channelaccording to processes described herein above. If the network devicewants to send frames with larger bandwidth such that it occupiessecondary 20 MHz, secondary 40 MHz, or secondary 80 MHz channel, thenthe network device uses the following process for the additionalchannels. If the secondary 20 MHz, secondary 40 MHz, or secondary 80 MHzchannel is available for a minimum duration time such as pointcoordination function (PCF) IFS (PIFS), short IFS (SIFS), or DIFS, thenthe network device assumes the secondary channel is available and mightinitiate a frame that covers the primary 20 MHz channel and thesecondary channel(s).

In some embodiments, there may be an adjustment made due to powermismatch between network devices. There is a chance that TX power of anetwork device and those network devices in its neighborhood might bedifferent. Hence, there is a chance that network device might be in theneighborhood of another network device, but that other network devicemay not be in the neighborhood of the implementing network device. Inthis situation, the implementing network device would realize that thetransmit power of the other network device is higher compared to its owntransmit power. This can be obtained by comparing the quantized TX powerindication that is carried in one of the SIG symbols that follows thePHY preamble in an 802.11 frame. If this situation is encountered,implementing network device, which already has detected framesoriginated from the other network device, and has assigned the othernetwork device to the neighboring network device set can use a lesssensitive threshold toward the captured frame destined to the othernetwork device, or even might assume the medium is not busy if othercriteria are met and prepare for transmission of its own frame afterinitiating the back off procedure etc.

In one embodiment, the adaptive threshold process has a TX-power-levelindication carried in the HE SIG symbol of each frame so that areceiving network device can approximately compare its own power withthat of the transmitting network device of the frame. ThisTX-power-level indication sub-field is a quantized indication and mighthave a few bits of length to indicate the transmit power that thetransmitting network device has used for the frame is within the rangeof e.g. P1 mW to P2 mW. By introducing such a sub-field in HE SIG-A orHE SIG-B, it is now required that this power indication is carried fromthe MAC entity to the PHY entity at the transmitter side and also fromthe PHY entity to the MAC entity at the receiving side. This is done byintroducing a parameter in TXVECTOR (sent from the MAC entity to the PHYentity at the transmitter side) and RXVECTOR (sent from the PHY entityto the MAC entity at the receiver side).

As an example, consider FIG. 1, where STA0 is the reference STA. WhenSTA0 is awake, it records the relevant IDs (TA/RA or PAIDs/BSSIDs andtheir short forms that might appear in PHY/PLCP header) of the framesthat captures. STA0 establishes the known relationship between thetransmitting and receiving IDs (PAID/PBSSID and their short forms). Thisprocessing is gradually updated whenever new IDs are collected. So aftera while STA0 realizes that the transmit IDs related to STAs 1-10 appearon the frames it has captured and infers that they are nearby, i.e.within −82 dBm-coverage of STA0. This constitutes the neighborhood listfor STA0. Subsequently, if STA0 captures a frame that its recipient isany of the STA 1-10, then STA0 would either (a) stick with CCA=−82 dBm,or (b) evaluates the situation by evaluating the average RSSI that hascaptured from each destination neighboring STA in past TBD_Tmax timeinterval, and if the RSSI is smaller than a RSSI_Th value, the STA mightadapt to a less sensitive CCA toward the captured frame and even mightassume the medium is available and initiates the back off procedure. IfSTA0 captures a frame sent by STA 1-10, but for a destination other thanSTA 1-10, then STA0 can adapt to CCA>−82 dBm (since STA0 knows that therecipient is outside of its −82 dBm-coverage).

Also note that the neighboring network device set is formed based on theframes that are captured on channels that include a primary channel.This is due to the requirement that all the frames that a STA sends andreceives at least occupy the primary 20 MHz channel. Hence, theneighboring network device set that is obtained as in previousparagraphs, is actually the neighboring network device set for theprimary channel. In general, the neighboring network device set for theprimary and secondary channels could potentially be different lists. Forinstance, a nearby STA denoted by STA1 might be operating only onsecondary 40 MHz channel and not at the primary 40 MHz channel. Thisleads to the result that STA1 would not appear in the neighbor list thatSTA0 has created based on its primary channel. In one embodiment, STA0evaluates the medium availability based on the primary channel using theneighboring network device set that is created from the moving historyof the frames exchanged on the primary channel. And, if STA0 wants tosend a frame wider than the primary 20 MHz channel, then it needs toobserve the availability of the secondary 20 MHz, secondary 40 MHz, andsecondary 80 MHz according to the rules specified in the spec. Althoughdescribed in relation to primary and secondary channels, the techniquesdescribed herein may be applied for any set of sub-channels.

FIG. 4 is a diagram of a network device implementing a station or accesspoint that executes an adaptive threshold process and a neighboringnetwork device set management process. In a wireless local area network(WLAN) such as the example WLAN illustrated in FIG. 7, a basic serviceset (BSS) includes a plurality of network devices referred to herein asWLAN devices. Each of the WLAN devices may include a medium accesscontrol (MAC) layer and a physical (PHY) layer according to IEEE(Institute of Electrical and Electronics Engineers) 802.11 standard. Inthe plurality of WLAN devices, at least one WLAN device may be an accesspoint (AP) station (e.g., access point 0 and access point 1 in FIG. 7)and the other WLAN devices may be non-AP stations (non-AP STAs), (e.g.,stations 0-3 in FIG. 7). Alternatively, all of the plurality of WLANdevices may be non-AP STAs in an Ad-hoc networking environment. Ingeneral, the AP STA and the non-AP STA may be each referred to herein asa station (STA). However, for ease of description, only the non-AP STAwill be referred to herein as a STA whereas the AP stations are referredto herein as APs for ease of description. As shown in FIG. 7, a WLAN canhave any combination of stations and access points that can formdiscrete network, an ad hoc network or any combination thereof. Anynumber of APs and stations can be included in a WLAN and any topologyand configuration of such APs and stations in the network can beutilized.

Also, there might be a field in one of SIG symbol(s) that follows thePHY preamble in an 802.11 frame that: (a) is set only by AP, (b)functions as an indication to whether AP allows or disallows itsassociated STAs to use adaptive threshold rules. This field could be asingle bit.

Referring to FIG. 4, the example WLAN device 1 includes a basebandprocessor 10, a radio frequency (RF) transceiver 20, an antenna unit 30,memory 40, an input interface unit 50, an output interface unit 60, anda bus 70. The baseband processor 10 performs baseband signal processing,and includes a MAC processor 11 and a PHY processor 15. These processorscan be any type of integrated circuit (IC) including a generalprocessing unit or an application specific integrated circuit (ASIC).

In one embodiment, the MAC processor 11 may include a MAC softwareprocessing unit 12 and a MAC hardware processing unit 13. The memory 40may store software (hereinafter referred to as “MAC software”),including at least some functions of the MAC layer. The MAC softwareprocessing unit 12 executes the MAC software to implement some functionsof the MAC layer and the MAC hardware processing unit 13 may implementthe remaining functions of the MAC layer in hardware (hereinafterreferred to “MAC hardware”). However, the MAC processor 11 is notlimited to this distribution of functionality.

The PHY processor 15 includes a transmitting signal processing unit 100and a receiving signal processing unit 200 described further hereinbelow with reference to FIGS. 5 and 6. In some embodiments, the PHYprocessor 15 can also implement the adaptive threshold module 300 and/orthe station set management module 400. The adaptive threshold module 300and the station set management module 400 can implement the respectivefunctions for any combination of the embodiments described herein abovewith regard to FIGS. 1-3, in one embodiment, the adaptive thresholdmodule 300 can implement the adaptive threshold process and the stationset management module 400 can implement the neighboring network deviceset management process. In other embodiments, these modules may beimplemented by or distributed over both the PHY processor 15 and the MACprocessor 11. These modules may be implemented as software or ashardware components of either the PHY processor 15 or MAC processor 11.These modules can be implemented as components of the transmittingsignal processing unit 100 and the receiving signal processing unit 200or as discrete components. In a further embodiment, the adaptivethreshold module 300 and/or the station set management module 400 can beimplemented by separate components or processors within the basebandprocessor.

The baseband processor 10, the memory 40, the input interface unit 50,and the output interface unit 60 may communicate with each other via thebus 70. The RF transceiver 20 includes an RF transmitter 21 and an RFreceiver 22. The memory 40 may further store an operating system andapplications. In some embodiments, the memory may store the nearbystations set. The input interface unit 50 receives information from auser and the output interface unit 60 outputs information to the user.

The antenna unit 30 includes one or more antennas. When a multiple-inputmultiple-output (MIMO) or a multi-user MIMO (MU-MIMO) system is used,the antenna unit 30 may include a plurality of antennas.

FIG. 5 is a schematic block diagram exemplifying a transmitting signalprocessor in a WLAN device. Referring to the above drawing, atransmitting signal processing unit 100 includes an encoder 110, aninterleaver 120, a mapper 130, an inverse Fourier transformer (IFT) 140,and a guard interval (GI) inserter 150. The encoder 110 encodes inputdata. For example, the encoder 110 may be a forward error correction(FEC) encoder. The FEC encoder may include a binary convolutional code(BCC) encoder followed by a puncturing device or may include alow-density parity-check (LDPC) encoder.

The transmitting signal processing unit 100 may further include ascrambler for scrambling the input data before encoding to reduce theprobability of long sequences of 0s or 1s. If BCC encoding is used inthe encoder 110, the transmitting signal processing unit 100 may furtherinclude an encoder parser for demultiplexing the scrambled bits among aplurality of BCC encoders. If LDPC encoding is used in the encoder 110,the transmitting signal processing unit 100 may not use the encoderparser.

The interleaver 120 interleaves the bits of each stream output from theencoder to change the order of bits. Interleaving may be applied onlywhen BCC encoding is used. The mapper 130 maps the sequence of bitsoutput from the interleaver to constellation points. If LDPC encoding isused in the encoder 110, the mapper 130 may further perform LDPC tonemapping in addition to constellation mapping.

When multiple input-multiple output (MIMO) or multiple user (MU)-MIMO isused, the transmitting signal processing unit 100 may use a plurality ofinterleavers 120 and a plurality of mappers 130 corresponding to thenumber N_(SS) of spatial streams. In this case, the transmitting signalprocessing unit 100 may further include a stream parser for dividingoutputs of the BCC encoders or the LDPC encoder into blocks that aresent to different interleavers 120 or mappers 130. The transmittingsignal processing unit 100 may further include a space-time block code(STBC) encoder for spreading the constellation points from the N_(SS)spatial streams into N_(STS) space-time streams and a spatial mapper formapping the space-time streams to transmit chains. The spatial mappermay use direct mapping, spatial expansion, or beamforming.

The IFT 140 converts a block of the constellation points output from themapper 130 or the spatial mapper to a time domain block (i.e., a symbol)by using an inverse discrete Fourier transform (IDFT) or an inverse fastFourier transform (IFFT). If the STBC encoder and the spatial mapper areused, the inverse Fourier transformer 140 may be provided for eachtransmit chain.

When MIMO or MU-MIMO is used, the transmitting signal processing unit100 may insert cyclic shift diversities (CSDs) to prevent unintentionalbeamforming. The CSD insertion may occur before or after the inverseFourier transform 140. The CSD may be specified per transmit chain ormay be specified per space-time stream. Alternatively, the CSD may beapplied as a part of the spatial mapper. When MU-MIMO is used, someblocks before the spatial mapper may be provided for each user.

The GI inserter 150 prepends a GI to the symbol. The transmitting signalprocessing unit 100 may optionally perform windowing to smooth edges ofeach symbol after inserting the GI. The RF transmitter 21 converts thesymbols into an RF signal and transmits the RF signal via the antennaunit 30. When MIMO or MU-MIMO is used, the GI inserter 150 and the RFtransmitter 21 may be provided for each transmit chain.

FIG. 6 a schematic block diagram exemplifying a receiving signalprocessing unit in the WLAN. Referring to FIG. 12, a receiving signalprocessing unit 200 includes a GI remover 220, a Fourier transformer(FT) 230, a demapper 240, a deinterleaver 250, and a decoder 260.

An RF receiver 22 receives an RF signal via the antenna unit 30 andconverts the RF signal into symbols. The GI remover 220 removes the GIfrom the symbol. When MIMO or MU-MIMO is used, the RF receiver 22 andthe GI remover 220 may be provided for each receive chain.

The FT 230 converts the symbol (i.e., the time domain block) into ablock of constellation points by using a discrete Fourier transform(DFT) or a fast Fourier transform (FFT). The Fourier transformer 230 maybe provided for each receive chain.

When MIMO or MU-MIMO is used, the receiving signal processing unit 200may use a spatial demapper for converting the Fourier transformedreceiver chains to constellation points of the space-time streams and anSTBC decoder for despreading the constellation points from thespace-time streams into the spatial streams.

The demapper 240 demaps the constellation points output from the Fouriertransformer 230 or the STBC decoder to bit streams. If LDPC encoding isused, the demapper 240 may further perform LDPC tone demapping beforeconstellation demapping. The deinterleaver 250 deinterleaves the bits ofeach stream output from the demapper 240. Deinterleaving may be appliedonly when BCC encoding is used.

When MIMO or MU-MIMO is used, the receiving signal processing unit 200may use a plurality of demappers 240 and a plurality of deinterleavers250 corresponding to the number of spatial streams. In this case, thereceiving signal processing unit 200 may further include a streamdeparser for combining the streams output from the deinterleavers 250.

The decoder 260 decodes the streams output from the deinterleaver 250 orthe stream deparser. For example, the decoder 100 may be an FEC decoder.The FEC decoder may include a BCC decoder or an LDPC decoder. Thereceiving signal processing unit 200 may further include a descramblerfor descrambling the decoded data. If BCC decoding is used in thedecoder 260, the receiving signal processing unit 200 may furtherinclude an encoder deparser for multiplexing the data decoded by aplurality of BCC decoders. If LDPC decoding is used in the decoder 260,the receiving signal processing unit 100 may not use the encoderdeparser.

A frame as used herein may refer to a data frame, a control frame, or amanagement frame may be exchanged between WLAN devices. The data frameis used for transmission of data forwarded to a higher layer. The WLANdevice transmits the data frame when the wireless medium is consideredto be in an idle condition or state such as after performing backoff ifa DIFS has elapsed from a time when the medium was not busy or undersimilar conditions. The management frame is used for exchangingmanagement information, which is not forwarded to the higher layer.Subtype frames of the management frame include a beacon frame, anassociation request/response frame, a probe request/response frame, andan authentication request/response frame. The control frame is used forcontrolling access to the medium. Subtype frames of the control frameinclude a request to send (RTS) frame, a clear to send (CTS) frame, andan acknowledgement (ACK) frame. In the case that the control frame isnot a response frame of the other frame, the WLAN device transmits thecontrol frame after performing backoff if the DIFS has elapsed. In thecase that the control frame is the response frame of the other frame,the WLAN device transmits the control frame without performing backoffif a short IFS (SIFS) has elapsed. The type and subtype of frame may beidentified by a type field and a subtype field in a frame control field.

On the other hand, a Quality of Service (QoS) STA may transmit the frameafter performing backoff if an arbitration IFS (AIFS) for an associatedaccess category (AC), i.e., AIFS[AC] has elapsed. In this case, the dataframe, the management frame, or the control frame, which is not theresponse frame, may use the AIFS[AC].

As discussed herein CCA and in particular as an embodiment of anadaptive threshold module is implemented to manage the transmission offrames by the WLAN device. CCA may implement a CSMA (carrier sensemultiple access)/CA (collision avoidance) based frame transmissionprocedure or similar procedure for avoiding collisions between frames ina channel.

FIG. 8 is a timing diagram providing an example of the CSMA/CAtransmission procedure. In the illustrated example, STA1 is a transmitWLAN device for transmitting data, STA2 is a receive WLAN device forreceiving the data, and STA3 is a WLAN device, which may be located atan area where a frame transmitted from the STA1 and/or a frametransmitted from the STA2 can be received by the WLAN device.

STA1 may determine whether the channel is busy by carrier sensing. TheSTA1 may determine the channel occupation based on a quality of thesignal on the channel or correlation of signals in the channel, or maydetermine the channel occupation by using a network allocation vector(NAV) timer.

When determining that the channel is not used by other devices duringDIFS (that is, the channel is idle), STA1 may transmit an RTS frame toSTA2 after performing backoff. Upon receiving the RTS frame, STA2 maytransmit a CTS frame as a response of the CTS frame after SIFS. WhenSTA3 receives the RTS frame, it may set the NAV timer for a transmissionduration of subsequently transmitted frames (for example, a duration ofSIFS+CTS frame duration+SIFS+data frame duration+SIFS+ACK frameduration) by using duration information included in the RTS frame. WhenSTA3 receives the CTS frame, it may set the NAV timer for a transmissionduration of subsequently transmitted frames (for example, a duration ofSIFS+data frame duration+SIFS+ACK frame duration) by using durationinformation included in the RTS frame. Upon receiving a new frame beforethe NAV timer expires, STA3 may update the NAV timer by using durationinformation included in the new frame. STA3 does not attempt to accessthe channel until the NAV timer expires.

When STA1 receives the CTS frame from the STA2, it may transmit a dataframe to the STA2 after SIFS elapses from a time when the CTS frame hasbeen completely received. Upon successfully receiving the data frame,the STA2 may transmit an ACK frame as a response of the data frame afterSIFS elapses.

When the NAV timer expires, STA3 may determine whether the channel isbusy through the use of carrier sensing techniques. Upon determiningthat the channel is not used by other devices during DIFS and after theNAV timer has expired, STA3 may attempt channel access after acontention window according to random backoff elapses.

The solutions provided herein have been described with reference to awireless LAN system; however, it should be understood that thesesolutions are also applicable to other network environments, such ascellular telecommunication networks, wired networks, and similarcommunication networks.

An embodiment may be an article of manufacture in which a non-transitorymachine-readable medium (such as microelectronic memory) has storedthereon instructions which program one or more data processingcomponents (generically referred to here as a “processor”) to performthe operations described above. In other embodiments, some of theseoperations might be performed by specific hardware components thatcontain hardwired logic (e.g., dedicated digital filter blocks and statemachines). Those operations might alternatively be performed by anycombination of programmed data processing components and fixed hardwiredcircuit components.

The PHY entity for IEEE 802.11 implemented in the WLAN device is basedon orthogonal frequency division multiple access OFDM or OFDMA. Ineither OFDM or OFDMA PHY layers, a STA is capable of transmitting andreceiving PPDUs that are compliant with the mandatory PHYspecifications. In a PHY specification, set of MCS and maximum number ofspatial streams are defined. Also in some PHY entities, downlink and/oruplink MU transmission with a maximum number of space-time streams peruser and up to a fix total number of space-time streams is defined.

FIG. 9 is a diagram of a very high throughput (VHT) PPDU utilized by theWLAN device PHY layer. FIG. 10 is a table of the fields of the VHT PPDU.Some PHY entities define PPDU that are individually addressed (whereidentification is based on AID or Partial AID) and some are groupaddressed (where identification is based on Group ID, GID). Some PHYentities provide support for 20 MHz, 40 MHz, 80 MHz and 160 MHzcontiguous channel widths and support for 80+80 MHz non-contiguouschannel width. The data subcarriers are modulated using binary phaseshift keying (BPSK), quadrature phase shift keying (QPSK), 16-quadratureamplitude modulation (16-QAM), 64-QAM and 256-QAM. Forward errorcorrection (FEC) coding (convolutional or LDPC coding) is used withcoding rates of 1/2, 2/3, 3/4 and 5/6.

In each PHY entity, there would be fields denoted as L-SIG, SIG-A, SIG-Bwhere some crucial information about the PSDU attributes are listed.These symbols are usually encoded with the most robust MCS. The L-SIG,SIG-A, SIG-B have very limited number of bits and it is desired toencode them in the most compact form possible. In a receiving STA, firstthese symbols are decoded in order to obtain vital information about thePSDU attributes and some MAC attributes. In IEEE 802.11 ac, thesesymbols are called VHT SIG-A and VHT SIG-B symbols.

As discussed above, WLAN devices are currently being deployed in diverseenvironments. These environments are characterized by the existence ofmany access points and non-AP stations in geographically limited areas.Increased interference from neighboring devices gives rise toperformance degradation. Additionally WLAN devices are increasinglyrequired to support a variety of applications such as video, cloudaccess, and offloading. In particular video traffic is expected to bethe dominant type of traffic in many high efficiency WLAN deployments.With the real-time requirements of some of these applications, WLANusers demand improved performance in delivering their applications,including improved power consumption for battery-operated devices.

IEEE 802.11 ax or HE SIG-A and IEEE 802.11 ax or HE SIG-B are referredto simply as simply by SIG-A and SIG-B and are amendments to the IEEE802.11 standard directed at addressing these problems. Unlike previousamendments where the focus was on improving aggregate throughput, thisamendment focuses on improving metrics that reflect user experience,such as average per station throughput, the 5th percentile of perstation throughput of a group of stations, and area throughput.Improvements will be made to support environments such as wirelesscorporate office, outdoor hotspot, dense residential apartments, andstadiums.

Some portions of the preceding detailed descriptions have been presentedin terms of algorithms and symbolic representations of operations ondata bits within a computer memory. These algorithmic descriptions andrepresentations are the ways used by those skilled in conferencingtechnology to most effectively convey the substance of their work toothers skilled in the art. An algorithm is here, and generally,conceived to be a self-consistent sequence of operations leading to adesired result. The operations are those requiring physicalmanipulations of physical quantities. It should be borne in mind,however, that all of these and similar terms are to be associated withthe appropriate physical quantities and are merely convenient labelsapplied to these quantities. Unless specifically stated otherwise asapparent from the above discussion, it is appreciated that throughoutthe description, discussions utilizing terms such as those set forth inthe claims below, refer to the action and processes of a conferencedevice, or similar electronic computing device, that manipulates andtransforms data represented as physical (electronic) quantities withinthe conference device's registers and memories into other data similarlyrepresented as physical quantities within the conference device'smemories or registers or other such information storage, transmission ordisplay devices.

Note the operations of the flowcharts are described with reference tothe exemplary embodiments of the diagrams. However, it should beunderstood that the operations of flowcharts can be performed byembodiments other than those discussed, and the embodiments of thediagrams can perform operations different than those discussed withreference to the flowcharts.

While the flowcharts in the figures herein above show a particular orderof operations performed by certain embodiments, it should be understoodthat such order is exemplary (e.g., alternative embodiments may performthe operations in a different order, combine certain operations, overlapcertain operations, etc.).

While the invention has been described in terms of several embodiments,those skilled in the art will recognize that the invention is notlimited to the embodiments described, can be practiced with modificationand alteration within the spirit and scope of the appended claims. Thedescription is thus to be regarded as illustrative instead of limiting.

What is claimed is:
 1. A method implemented by a first network device,the method to provide an adaptive clear channel assessment (CCA) processin a wireless local area network (WLAN) to determine availability of awireless channel in the WLAN, the method comprising: detecting, by thefirst network device, a wireless signal from a second network device ona wireless medium; determining whether a target network device of thewireless signal is a neighbor of the first network device; and comparinga target device threshold with one or more signal quality valuesassociated with transmissions of the target network device in responseto determining that the target network device is a neighbor of the firstnetwork device.
 2. The method of claim 1, further comprising:determining that the wireless medium is busy in response to determiningthat the one or more signal quality values are greater than the targetnetwork device threshold.
 3. The method of claim 1, further comprising:determining that the wireless medium is idle in response to determiningthat the one or more signal quality values are less than the targetnetwork device threshold.
 4. The method of claim 1, further comprising:comparing a signal quality of the wireless signal with a CCA threshold;and determining that the wireless medium is idle in response to thesignal quality of the wireless signal being below the CCA threshold. 5.The method of claim 1, further comprising: determining whether aconfidence level has been reached for the target network device, wherethe confidence level indicates a predetermined number of received framesin a time period have been collected from the target network device topresent an accurate representation of the target network device relativeto the first network device, wherein the comparing the target devicethreshold with one or more signal quality values associated withtransmissions of the target network device is performed in response todetermining that the confidence level has been reached.
 6. The method ofclaim 5, further comprising: determining the wireless medium is busy inresponse to determining that the confidence level has not been reached.7. The method of claim 1, wherein the one or more signal quality valuesis a running average associated with signal quality of wirelesstransmissions of the target network device.
 8. The method of claim 1,wherein the wireless signal is a multi-user signal, the method furthercomprising: determining that the wireless medium is idle when one ormore target devices of the wireless signal is not a neighbor of thefirst network device.
 9. The method of claim 1, further comprising:determining that the first network device has not received a wirelesssignal from the target network device in a predetermined time period;and determining that the wireless channel is idle in response todetermining that the first network device has not received a wirelesssignal from the target network device in the predetermined time period.